Well Abdu’l-Baha made some pretty obvious mistakes regarding simple physical matters. For instances, he believes both concave and convex mirrors focus light in a real spot that creates intense heat:

“Like sunlight that does not have a complete effect on a flat mirror, but when it shines on a concave or convex mirror, all its heat is focused in a single point and the heat of that point will become stronger than fire,” Abd al-Hamid Ishraq Khawari, Ayyam tis`a, p. 324 (citing Abdu’l-Baha)

Or claims that minerals contain a spirit of life and that all materialistics agree to this:

“As to the existence of spirit in the mineral: it is indubitable that minerals are endowed with a spirit and life according to the requirements of that stage. This unknown secret, too, hath become known unto the materialists who now maintain that all beings are endowed with life,” Abdu’l-Baha, Tablet to August Forel, p. 9.